Magnetic resonance imaging, computed tomography, and 68Ga-DOTATOC positron emission tomography for imaging skull base meningiomas with infracranial extension treated with stereotactic radiotherapy - a case series

Fifty patients with 56 meningiomas of the SB underwent MRI, CT, and 68Ga-DOTATOC PET/CT prior to fractionated stereotactic radiotherapy. The study group consisted of 16 patients who had infracranial meningioma extension, visible on MRI ± CT (MRI/CT) or PET, and were evaluated further. The respective findings were reviewed independently, analyzed with respect to correlations, and compared with each other.Within the study group, SB transgression was associated with bony changes visible by CT in 14 patients (81%). Tumorous changes of the foramen ovale and rotundum were evident in 13 and 8 cases, respectively, which were accompanied by skeletal muscular invasion in 8 lesions. We analysed six designated anatomical sites of the SB in each of the 16 patients. Of the 96 sites, 42 had infiltration that was delineable by MRI/CT and PET in 35 cases and by PET only in 7 cases. The mean infracranial volume that was delineable in PET was 10.1 ± 10.6 cm3, which was somewhat larger than the volume detectable in MRI/CT (8.4 ± 7.9 cm3).68Ga-DOTATOC-PET allows detection and assessment of the extent of infracranial meningioma invasion. This method seems to be useful for planning fractionated stereotactic radiation when used in addition to conventional imaging modalities that are often inconclusive in the SB region.Meningiomas are common intracranial tumours with 25 to 30% located at the skull base (SB) [1]. When originating from the anterior clinoid process or medial sphenoid wing, they have an increased propensity to invade bone [2], which is a strong risk factor for recurrence [3]. Meningiomas in this location tend to progress transcranially or invade the infracranial spaces via natural openings [2,4] and recur in up to 45% of cases after surgery [5]. There is a strong correlation between the extent of resection and rate of recurrence [6]; therefore, accurate determination of tumour extension is critical for planning the magnitude of surgery and/or radiotherapy.Computed tomography (C